Shidaowan unit 1 reaches key milestone as inner safety dome installed

China Huaneng has installed the inner safety dome on the containment building of Shidaowan unit 1, a clear sign that the project has moved out of major civil construction and into the equipment installation phase. The hyperboloid dome, built from 70 wall panels and weighing 227.9 tonnes, was hoisted into position on 25 April 2026. For a project this size, containment closure is more than a visual milestone: it narrows the path to commissioning.

Shidaowan unit 1 is the first of four HPR1000, or Hualong One, reactors planned for the site in Shandong Province. The project was approved by the State Council of the People’s Republic of China at an executive meeting on 31 July 2023, first concrete for unit 1 was poured in July 2024, and first concrete for unit 2 followed in May 2025. China Huaneng has said the first phase is scheduled to be completed and put into operation in 2029, giving the site a defined build-out window even as work now shifts toward the long run of installation and testing.

The containment building uses a double-layer design intended to preserve integrity and leak tightness and to help retain radioactive substances. Once the inner dome is in place, the next milestones usually move through the rest of containment closure, major equipment set, pipework and cabling, integrated system testing, hot functional testing, fuel loading and then first grid connection. In that sequence, the inner dome is one of the clearest markers that a reactor unit is leaving the heavy civil stage behind and heading toward pre-operational work.

The pace so far looks broadly in line with a large Chinese multi-unit build rather than an abrupt acceleration. Roughly 21 months passed between first concrete on unit 1 and the inner dome installation, while unit 2 followed 10 months after unit 1’s first concrete. That is the kind of steady, repeatable cadence that tends to matter most on a fleet-build site, where the commercial signal comes not from one-off spectacle but from how consistently the next unit advances.

Shidaowan is already becoming one of China’s most important nuclear campuses. The site’s HTR-PM demonstration reactor, described as the world’s first modular high-temperature gas-cooled reactor nuclear power plant, first generated power in December 2021 and entered commercial operation in December 2023. The first of two Guohe One demonstration reactors was connected to the grid in November 2024. China Huaneng has described the site as a nuclear power base combining both third-generation and fourth-generation technologies, and the four-unit Hualong One project is meant to deepen that mix.

When the full Shidaowan base is completed, China Huaneng says it should generate about 35 billion kilowatt-hours of electricity a year, enough for roughly 17 million three-person households. At that scale, the inner dome on unit 1 is not just a construction lift. It is a marker that one more reactor on this multi-technology site is moving closer to the point where concrete turns into megawatts.